The present invention relates generally to fuel pumps of the type having a high pressure pump with one or more reciprocating pumping plungers for periodically delivering fuel at high pressure for fuel injection. Such a pump is referred to herein as a "Reciprocating Fuel Pump". The present invention relates more particularly to a Reciprocating Fuel Pump having a new and improved fuel transfer pump for transferring fuel intermittently to the high pressure pump.
The present invention has notable utility in a Reciprocating Fuel Pump of the type having a rotatable cam for reciprocating the pumping plungers (normally in synchronism with an associated internal combustion engine). Such a pump is referred to herein as a "Rotatable Cam Type Fuel Pump". For example, the present invention has notable utility in a Rotatable Cam Type Fuel Pump of the kind having a pump body with a plurality of radial pumping plungers and a cam ring surrounding the pump body and rotatable for reciprocating the pumping plungers. Such a pump is referred to herein as a "Rotatable Cam Ring Type Fuel Pump". U.S. Pat. No. 5,318,001, dated Jun. 7, 1994 and entitled "Distributor Type Fuel Injection Pump" discloses an example of a Rotatable Cam Ring Type Fuel Pump.
The present invention has utility in Reciprocating Fuel Pumps of both the distributor type (i.e., which deliver high pressure charges of fuel directly and sequentially to the fuel injectors of an associated engine) and non-distributor type (e.g., which deliver fuel at high pressure to a common rail fuel injection system). The present invention also has utility in Reciprocating Fuel Pumps other than Rotatable Cam Type Fuel Pumps and which for example have a fixed cam and rotatable pump body instead of a rotatable cam and fixed pump body.
In accordance with a principal aim of the present invention, a Reciprocating Fuel Pump is provided with a transfer pump for transferring fuel intermittently to the high pressure pump in timed relationship with the reciprocating pumping plungers. The transfer pump is operated at the same frequency as the high pressure pump and in synchronization with the high pressure pump so that the intermittent transfer phase of operation of the transfer pump occurs during the intermittent intake phase of operation of the high pressure pump. Optimum synchronization of the transfer pump and high pressure pump is established so that the transfer pump meets the fuel demand of the high pressure pump throughout the full range of speed and delivered fuel volume of the high pressure pump.
Another aim of the present invention is to provide in a Rotatable Cam Ring Type Fuel Pump, a new and improved transfer pump synchronized with the high pressure pump to transfer fuel intermittently to the high pressure pump uniformly and without cavitation.
Another aim of the present invention is to provide in a Reciprocating Fuel Pump, a new and improved transfer pump synchronized with the high pressure pump to transfer fuel intermittently to the high pressure pump with increased efficiency and lower drive torque.
Another aim of the present invention is to provide in a Rotatable Cam Ring Type Fuel Pump, a new and improved cam operated transfer pump integrated into the fuel pump with significantly less mechanical and hydraulic complexity than vane type transfer pumps conventionally employed in such fuel pumps.
Another aim of the present invention is to provide in a Rotatable Cam Ring Type Fuel Pump, a new and improved cam operated transfer pump and a new and improved oil system for lubricating the cam and cam follower mechanisms of the transfer pump and high pressure pump. In accordance with this aim, the fuel pump has an internal oil system connected to receive oil from and return oil to the associated engine without fuel contamination of the oil.
Another aim of the present invention is to provide in a Rotatable Cam Ring Type Fuel Pump, a new and improved cam operated transfer pump for transferring fuel intermittently to the high pressure pump and a new and improved cam operated supply pump integrated with the transfer pump for supplying fuel intermittently to the transfer pump.
A further aim of the present invention is to provide in a Reciprocating Fuel Pump, a new and improved transfer pump synchronized with the high pressure pump to transfer fuel intermittently to the high pressure pump in optimum synchronism with the intermittent fuel demand of the high pressure pump throughout the full range of speed and delivered fuel volume of the high pressure pump.
Another aim of the present invention is to provide a new and improved Rotatable Cam Ring Type Fuel Pump which can be more economically manufactured; which provides oil lubrication of the rotatable cam and cam follower mechanisms of the pump to permit the delivery of fuel from the high pressure pump at 16,000 psi and higher; which can be used with internal combustion engines having two to eight cylinders or more; and which is electrically controlled to precisely regulate the volume and/or timing of the high pressure delivery of fuel by the pump.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
A better understanding of the invention will be obtained from the following detailed description and the accompanying drawings of illustrative embodiments of the invention.